Add tox.ini with some basic runners

.bandit.yml

+skips:
+- B603  # Ignore warnings about calling subprocess.Popen without shell=True
+- B607  # Ignore warnings about calling subprocess.Popen without a full path to executable

tox.ini

+[tox]
+minversion = 3.5.0
+envlist = unittest, docs, bandit, build
+
+[testenv]
+basepython = python3
+usedevelop = True
+setenv =
+   VIRTUAL_ENV={envdir}
+   PYTHONWARNINGS=default::DeprecationWarning
+install_command = pip install {opts} {packages}
+
+[testenv:unittest]
+deps =
+  discover
+  -r{toxinidir}/devel-requirements.txt
+  -r{toxinidir}/requirements.txt
+commands = discover -s tests
+
+[testenv:cover]
+setenv =
+   {[testenv]setenv}
+   PYTHON=coverage run --parallel-mode
+deps =
+    coverage
+    discover
+commands = coverage erase
+           coverage run --source pyasn1 -m unittest discover {posargs}
+           coverage report --fail-under 80
+
+[testenv:bandit]
+skip_install = true
+deps =
+    bandit
+commands =
+    bandit -r pyasn1 -c .bandit.yml
+
+[testenv:docs]
+commands = make -C docs html
+
+[testenv:build]
+skip_install = true
+deps =
+    wheel
+    setuptools
+commands =
+    python setup.py -q sdist bdist_wheel